The basic operation and structure of a land mobile radio system is well known. Land mobile radio systems typically comprise one or more radio communication units and one or more repeaters, also known as base stations, that transceive information via the RF communication resources. These communication resources may be narrow band frequency modulated channels, time division multiplex slots, frequency pairs, and so forth. Land mobile radio systems may be organized as trunked communication systems, where a plurality of communication resources is allocated amongst a group of users by assigning the repeaters on a communication-by-communication basis with an RF coverage area.
Currently, there is a desire to have larger communication systems that cover much larger geographic areas. Today, communication systems are known to be organized into a plurality of communication sites, as shown in FIG. 1, with a zone or network controller (ZC) attached to a bank of repeaters 103 at each of the sites S1, S2, S3, S4, S5, and S6 so that communication requests from a communication unit 105 within a coverage area 101 may be handled and organized amongst all of the sites that are connected to that zone controller. These repeaters may be intelligent repeaters, such as an IntelliRepeater.TM. available from Motorola, Inc., and the zone controller communicates with the intelligent repeater that is currently in control of the site. Alternatively, the repeaters may be standard repeaters with a site controller (not shown) attached to the each of the repeaters at the site, and the site controller coordinates and controls resources for the site. Although many more repeaters and sites may be present in an actual communication system, only five repeaters and six sites are shown for the sake of simplicity of the drawings. There is, however, a limit to the number of site that can be serviced by one zone controller. Consequently, a need exists for a way to cover larger areas of land while still maintaining control in a single communication system. Today, RF or wireline intersystem communication paths can be established on an as needed basis. These intersystem communication paths are established between independent communication systems, and are disconnected when no longer needed. Other systems. utilize dedicated lines that link communication systems continuously, although such an implementation is inefficient, as these dedicated lines tend to remain idle for a good part of the time.
Accordingly, there is a need for a communication system that efficiently covers a large area while maintaining centralized control for the entire area.